Enhancement

• QoS and Retain flag in rule engine's message republish actions can now use placeholders
• Supports exclusive subscriptions, that is, only one subscriber is allowed for a topic
• Dashboard and management API's HTTPS listeners can now use password-protected private key files, providing key_password configuration item
• Support for placeholders %u and %c in topic rewrite rules
• Optimize the UI when creating rule engine resources, such as folding some uncommon options, etc.
• Opened 4 TCP-related configuration items: KeepAlive, TCP_NODELAY, SO_RCVBUF and SO_SNDBUF for the underlying gRPC connection of ExHook

Bug fixes

• Fix the issue of inaccurate memory calculation in Linux OS, and calculate the memory usage of the current OS instead of the memory usage of EMQX
• Fix the issue that the old disconnect event of ExHook would be triggered later than the new connect event when the client reconnects
• Fix the issue that the execution order of topic rewriting and delayed publish is not fixed, now it is fixed to execute topic rewriting first
• Fix the issue that rule engine could not encode MQTT 5.0 user properties
• Fix the issue that the count of connack.auth_error is inaccurate when the client uses a protocol version below MQTT v5.0 to access
• Fix the issue that the UDP listeners of LwM2M and CoAP gateways could not bind to the specified network interface
• Fix Dashboard not starting after removing the default Dashboard user in the configuration file
• Fix client.subscribe hook not being able to reject subscriptions
• If the placeholder in the ACL rule is not replaced, the client's publish or subscribe operation will be rejected